The present invention relates to a gauge for monitoring the filtering performance of a vehicle filter. More specifically, the present invention relates to a low cost, simplified gauge for helping vehicle owners determine whether their air filter needs replacement.
Air filter restriction gauges are used in connection with an air filter for internal combustion engines. These devices typically sense the level of airflow restriction, and provide an indication of this restriction level by providing some type of display. When the air filter has become so loaded with contaminants that the supply of air required by the engine for its operating efficiency is not being drawn through the filter, the gauge will indicate this and thus alert the operator that the filter requires cleaning or replacement. Some existing devices will also lock themselves in various positions to provide a continuous indication as to how much useful life remains in the air filter before it should be cleaned or changed.
The use of a gauge to monitor the filtering ability of a vehicle's air filter is known in the art. Earlier patents in this area include U.S. Pat. No. 4,369,728, issued to Nelson on Jan. 25, 1983, and U.S. Pat. No. 4,445,456, issued to Nelson on May 1, 1984. These devices provided an incremental visual display to the users or maintenance personnel.
Air filter restriction indicator gauges have been available for quite some time. Initially, these indicator gauges were simply a single stage type gauge where a warning button would pop-up once a predetermined restriction level was achieved. The pop-up type gauges were not believed to be reliable and typically not trusted. The design of these gauges was complex and prone to many variations in performance. Also, this pop-up type gauge was difficult to manufacture due to the number of parts required and the intricacies of their assembly.
Additionally, prior art indicators have not always been easy to fully reset, sometimes resulting in a gauge that may give a false, premature signal that an air filter requires replacement. These false signals result in unnecessary filter maintenance--precisely what the gauge is intended to avoid.
In order to accommodate the locking features of prior indicator gauges, previous systems have required fairly involved and complex lock up mechanisms. Often these gauges comprise separate hinged locking pins which must be appropriately attached and aligned within the gauge. As expected, this has provided a manufacturing challenge to accomplish this necessary alignment. As can be easily appreciated, these types of structures also involve additional steps to assemble.
As most gauges have a locking feature so as to indicate that the predetermined vacuum level has been achieved, it is also necessary to provide reset capabilities. This provides additional design challenges when the lock pin is configured. More specifically, the lock pin must be accessible from the back side. Ideally, the button is depressed to unlock the mechanism. This resetting feature of previous designs which have a separate hinged locking pin structure makes the gauges more complex and costly to fabricate.